Mitigation and Remedy of Groundwater Arsenic Menace in India

Mitigation and Remediation Update from West Bengal and Bihar : Studies and Projects Initiatedb) Maintenance of water treatment units: Periodical maintenance of water treatmentunits, generally installed at various sites, requires a close monitoring. Efficacy of anytreatment unit depends not only on the merit of technology but also on the regularmaintenance and vigilance.c) Networking/Transportation: A long transportation is required for supply of surfacewater from intake point/ treatment unit to the delivery points, particularly in the areaswhere water is to be supplied. This would involve: i) maintenance to avoid leakagedamage in pipe lines during transportation ii) considerable cost of pipe line & itsmaintenance, iii) upholding of pressure for long transportation, etc.d) Acceptability of using surface water for drinking purposes: Generally, rural peopleare habitual in using groundwater for drinking purposes and use of treated surfacewater, specially chlorinated water & its smell, is not conventionally practiced. Therefore, switching over from routine groundwater uses to surface water sources,particularly for potable water would need an effort for social empowerment.4.1.5 Uses of arsenic free groundwater by tapping deep aquifersThe arsenic contaminated zones mostly lie within the shallow aquifer (100 m bgl) underneath thecontaminated shallow aquifer, in many places of Bengal Delta Plains, are normally seen arsenicfree. The deeper aquifer is separated by a thick clay layer of appropriate composition from theshallow aquifer. From the isotopic studies carried out in West Bengal, it is observed that there isno hydraulic connection between the shallow and deep aquifers as they belong to different agegroups. Those deep arsenic free aquifers have the potential to yield nearly 5 to 20 lps of water,which is largely adequate to meet demand of water in the domestic sector. It is observed in thefield studies that properly designed tube wells are capable to harness deeper arsenic free aquiferwithout posing any future threat of arsenic mobilization from the overlain contaminated zone.Similar experiences are observed from coastal areas where fresh deeper aquifer is separatedfrom upper saline/brackish water by a thick clay layer. For example number of wells constructedusing cement sealing techniques could yield fresh water for a very long period. However, insome cases, the deep tube wells are reported to be contaminated with arsenic, which might haveattributed due to the following reasons:(i) Tube wells constructed in the past might have not been properly designed with cementsealing techniques,(ii) Tube wells constructed in the past might have been designed to screen both the upperand deeper aquifer to get higher discharge,(iii) Tube wells constructed with cement sealing might have not been constructed properly.64NIH & CGWB